It is common for a network-accessible service to monitor the activity of a user who is interacting with the service. In one typical case, the service can deliver content to a user that includes various selectable features. The service can then register the user's express selection of these features. For instance, the service can deliver a page of content that includes one or more advertisements. The service can record each time the user selects these advertisements, such as by clicking on these advertisements or making some other express action that is directed at these advertisements. This type of monitoring can be performed for a collection of users to provide a general measure of how effective the features are in achieving a desired end result, such as eliciting the user's selection of the features. Such measurements, in turn, can be used to better assess the value of the features (for example, to better set the price charged for advertisements). In another typical case, the service can monitor the manner in which a user navigates from page to page within the service, such as by clicking on a link which activates a new page.
A user can be said to consume content by engaging or interacting with the content in any manner. One way of consuming content is by making the above-described types of express actions within a page, such as by clicking on various features in the content. However, a user's consumption of network-delivered content may not always be adequately represented by the user's mouse clicks or the user's movement from page to page within the content. In some cases, for example, a user may examine a part of a page, yet may not perform any express action with respect to that part. For example, the user may study a feature within the page, yet fail to click on this feature; this may be because the feature is non-selectable or the user simply declines to click on the feature. The feature nonetheless can be considered successful in engaging the user. Known techniques do not provide a suitably efficient mechanism for monitoring the user's consumption of content in these types of circumstances. As a result, a network-accessible service may fail to generate a sufficiently accurate understanding of how the user is engaging the service. As a further result, the service may fail to efficiently utilize and/or price its resources.